NASA’s Marshall Space Flight Center (MSFC) developed Ultrasonic Stir Welding (USW) to join large pieces of very high-strength metals such as titanium and Inconel. USW, a solid-state weld process, improves current thermal stir welding processes by adding high-power ultrasonic (HPU) energy at 20-kHz frequency. The addition of ultrasonic energy significantly reduces axial, frictional, and shear forces; increases travel rates; and reduces wear on the stir rod, which results in extended stir rod life. The USW process decouples the heating, stirring, and forging elements found in the friction stir welding process, allowing for independent control of each process element and, ultimately, greater process control and repeatability. Because of the independent control of USW process elements, closed-loop temperature control can be integrated into the system so that a constant weld nugget temperature can be maintained during welding.

A diagram of the basic components of the Ultrasonic Stir Welding technology.

Ultrasonic Stir Welding is a solid-state stir welding process, meaning that the weld workpiece does not melt during the welding process. The process uses a stir rod to stir the plasticized abutting surfaces of two pieces of metallic alloy that form the weld joint. Heating is done using a specially designed induction coil. The control system has the capability to pulse the HPU energy of the stir rod on and off at different rates from 1-second pulses to 60-millisecond pulses. This pulsing capability allows the stir rod to act as a mechanical device (moving and stirring plasticized nugget material) when the HPU energy is off, and allowing the energized stir rod to transfer HPU energy into the weld nugget (to reduce forces, increase stir rod life, etc.) when the HPU energy is on. The process can be used to join high-melting-temperature alloys such as titanium, Inconel, and steel.

Potential uses include hardware for severe environments, launch vehicles, and aircraft in aerospace applications; pistons, struts, and vehicle structure in automotive applications; shipbuilding and platforms in marine applications; and bridges, trains, and pressure vehicles in civil applications.

NASA is actively seeking licensees to commercialize this technology. Please contact Sammy A. Nabors at This email address is being protected from spambots. You need JavaScript enabled to view it. to initiate licensing discussions. Follow this link for more information: http://technology.nasa.gov/patent/TB2016/TOP8-95 .


NASA Tech Briefs Magazine

This article first appeared in the January, 2017 issue of NASA Tech Briefs Magazine.

Read more articles from this issue here.

Read more articles from the archives here.